EP0406424A1 - Process for recovering crystals from slurry - Google Patents

Process for recovering crystals from slurry Download PDF

Info

Publication number
EP0406424A1
EP0406424A1 EP89906439A EP89906439A EP0406424A1 EP 0406424 A1 EP0406424 A1 EP 0406424A1 EP 89906439 A EP89906439 A EP 89906439A EP 89906439 A EP89906439 A EP 89906439A EP 0406424 A1 EP0406424 A1 EP 0406424A1
Authority
EP
European Patent Office
Prior art keywords
slurry
crystals
pressure
filtrate
filter medium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP89906439A
Other languages
German (de)
French (fr)
Other versions
EP0406424A4 (en
EP0406424B1 (en
Inventor
Masanori Mitsui Petrochemical Ind. Ltd. Ueda
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsui Chemicals Inc
Original Assignee
Mitsui Petrochemical Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsui Petrochemical Industries Ltd filed Critical Mitsui Petrochemical Industries Ltd
Publication of EP0406424A1 publication Critical patent/EP0406424A1/en
Publication of EP0406424A4 publication Critical patent/EP0406424A4/en
Application granted granted Critical
Publication of EP0406424B1 publication Critical patent/EP0406424B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/06—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/06—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums
    • B01D33/073—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums arranged for inward flow filtration
    • B01D33/09—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums arranged for inward flow filtration with surface cells independently connected to pressure distributors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/06—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums
    • B01D33/073—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums arranged for inward flow filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/44—Regenerating the filter material in the filter
    • B01D33/48—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
    • B01D33/50—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps with backwash arms, shoes or nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/58—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element
    • B01D33/60—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for washing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/58—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element
    • B01D33/62—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying
    • B01D33/66—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying by gases or by heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/70—Filters with filtering elements which move during the filtering operation having feed or discharge devices
    • B01D33/76—Filters with filtering elements which move during the filtering operation having feed or discharge devices for discharging the filter cake, e.g. chutes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/80—Accessories
    • B01D33/804—Accessories integrally combined with devices for controlling the filtration
    • B01D33/808—Accessories integrally combined with devices for controlling the filtration by pressure measuring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D37/00—Processes of filtration
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/42—Separation; Purification; Stabilisation; Use of additives
    • C07C51/47—Separation; Purification; Stabilisation; Use of additives by solid-liquid treatment; by chemisorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2201/00—Details relating to filtering apparatus
    • B01D2201/28—Position of the filtering element
    • B01D2201/282—Filtering elements with a horizontal rotation or symmetry axis

Definitions

  • the present invention relates to a method for recovering crystals from a slurry containing crystals of, such as terephthalic acid.
  • terephthalic acid produced will deposit within the mother liquor as crystals forming a slurry containing crystals of terephthalic acid.
  • a crude product of terephthalic acid is obtained.
  • terephthalic acid is caused to deposit as crystals to form a slurry containing the crystals.
  • purified terephthalic acid is obtained.
  • the slurry has heretofore been subjected to procedures of separating the crystals by filtration or by centrifugation, washing the so separated crystals by re-slurrying in a wash liquor, separating again the crystals from this re-slurry and, if necessary, repeating these operations.
  • Such a conventional technique reveals disadvantages that the procedures are complicated and that a larger apparatus has to be installed therefor.
  • the object of the present invention is to obviate the disadvantage mentioned above and to propose a novel method for recovering crystals from a slurry under the use of RVF, which enables to recover the crystals by effecting a sequence of operations of filtration, washing and further filtration without suffering from stuffing of the filter medium.
  • the present invention proposes a method for recovering crystals from a slurry by supplying the slurry to a rotary vacuum filter while rotating a cylindrical filter medium thereof to effect a sequence of operations of sucking filtration, washing and further sucking filtration, said method comprising conducting a sucking filtration while pressurizing the slurry side so as to maintain such a temperature and pressure that the filtrate of the rotary vacuum filter will not reach a condition of supersaturation.
  • the present invention incorporates a sucking filtration under a pressurized condition, in order to avoid the supersaturation of the mother liquor as mentioned above.
  • the sucking filtration in the RVF is carried out while pressurizing the slurry side on the rotating filter medium so as to maintain such a temperature and pressure that the filtrate of the rotary vacuum filter will not reach a condition of supersaturation.
  • a premature stuffing of the filter medium due to the deposition of crystals from the mother liquor together with an increase in the viscosity of the-slurry is eliminated and the crystals can be recovered from the slurry at higher efficiency over a considerable long period of time.
  • numeral 1 indicates an RVF housed by a casing 2 in which a horizontal cylindrical filter medium 3 is disposed in freely rotatable manner.
  • the lower part of the filter medium 3 is soaked in a sump of slurry 4 formed inside the lower part of the casing 2 to form a filtering region 5, inside which there is provided an exhaustion unit 8 for sucking out internal gas 7 and the accumulated filtrate 6.
  • a spray unit 10 for spraying the wash liquor onto the filtered cake 9.
  • the filter medium 3 has a washing region 11 and, subsequent thereto, a de-liquoring region 12, inside which there is provided a collecting section 13 where the wash liquor is collected.
  • 17 denotes a slurry supply inlet, 18 a slurry accumulater, 19 a cake accumulator and 20 a gas inlet for regulating the pressure.
  • 21 is a slurry reservoir from which the slurry is supplied to the RVF 1 at the slurry supply inlet 17 by a pump 22, while recirculating the slurry via the slurry accumulator 18.
  • 23 is a control valve for keeping the liquid level in the slurry reservoir 21 constant and 24 is a control valve for maintaining the liquid level in the slurry accumulator 18 fixedly.
  • 25 is a control exhaustion valve for exhausting the gas so as to maintain the internal pressure in the slurry reservoir 21.
  • 26 is a condenser.
  • 27 is a slurry make-up inlet.
  • 28 is a wash waste tank in which the spent wash liquor collected in the collecting section 13 is accumulated and from which it is exhausted out of the system by a pump 29.
  • 30 is a control valve operative so as to keep the liquid level in the wash waste tank 28 constant.
  • 31 is a filtrate storage receiving the filtrate 6 and the gas 7 sucked out from the exhaustion unit 8 and exhausting the filtrate 6 by a pump 32.
  • 33 is a level control valve operative for maintaining a constant liquid level in the filtrate storage 31.
  • the gas in the wash waste tank 28 and in the filtrate storage 31 is passed to a condenser 34 to effect condensation, the drain of which is separated by a drain separator 35 and the liquid phase separated is turned back to the filtrate storage 31, whereupon the gas is compressed by a compressor 36 and is then supplied to the gas inlet 20 as the pressure control gas.
  • 37 is a pressure control valve operative so as to maintain a constant pressure of the pressure control gas.
  • 38 is a drier which serves for drying the cake 9 discharged from the cake accumulator 19 via two closure valve means 39 and 40, from which it is taken out as refined crystals (product of manufacture).
  • the slurry 4 stored in the slurry reservoir 21 is supplied to the sump of RVF 1 by a pump 22 and the filter medium 3 is caused to rotate so as to effect, in succession, the steps of sucking filtration, washing, sucking de-liquoring and removal of the washed cake.
  • the compressed gas for controlling the filtration pressure is supplied via the gas inlet 20 to pressurize the slurry side 4, in order to maintain the filtrate 6 at such a pressure and temperature that no supersaturation thereof occurs, while sucking out the filtrate 6 and the gas 7 from the exhaustion unit 8 to effect sucking filtration in the filtering region 5.
  • the pressure on the side of the slurry corresponds to the sum of the filtering pressure drop and the pressure on the side of the filtrate.
  • a sucking filtration is realized thereby, wherein the crystals suspending in the slurry 4 are retained on the rotating filter medium 3 and forms a layer of filtered cake 9 guided upwards, while a part of the slurry 4 is recirculated from the slurry accumulator 18 to the slurry reservoir 21.
  • Filtered cake 9 is washed in the washing region 11 by a wash liquor sprayed from the spray unit 10 and passes then to the de-liquoring region 12, where the wash liquor is removed, and turns downwards.
  • a blowing gas is supplied to the gas supply part 16 and is caused to blow out from the blowing horn 14 to remove the cake 9.
  • the filtrate 6 and the gas 7 sucked out of the exhaustion unit 8 are introduced into the filtrate storage 31, from which the filtrate 6 is exhausted by the pump 32.
  • the spent wash liquor exhausted from the collecting section 13 is introduced into the wash waste tank 28, from which it is discharged out of the system by the pump 29.
  • the gas accumulating in the wash waste tank 28 and in the filtrate storage 31 is passed via the condenser 34 to the drain separator 35, whereupon the gas separated from the condensed drain is compressed by the compressor 36 and the thus compressed gas is served for the filtration pressure control gas and is supplied to the gas inlet 20 to pressurize the side of the slurry 4 of the RVF 1.
  • the cake 9 removed in the cake removal zone 15 is taken out through the two closure valves 39 and 40 and is dried in the drier 38, before it is recovered therefrom as purified crystals (product of manufacture).
  • a slurry of terephthalic acid/acetic acid (with 40 % by weight of terephthalic acid, at 120 1C) resulting from an industrial production of terephthalic acid was treated by the method illustrated in the appended Figs. to recover crude terephthalic acid crystals.
  • the slurry side in the RVF was maintained at a pressure of 1.5 Kg/cm 2 abs. at 120 °C and the filtrate side at a pressure of 1 Kg/cm 2 abs. at 120 °C.
  • the operation duration of the RVF until occurrence of stuffing of the filter medium was found to be 50 hours.
  • Example 1 The procedures of Example 1 were repeated under a modification of the condition that the slurry side in the RVF 1 was maintained at the atmospheric pressure and at a temperature of 120°C and the filtrate side was held at a pressure -400 mmHg lower than the atmospheric pressure and at a temperature of 100 °C.
  • the operation duration of the RVF until occurrence of stuffing of the filter medium was found to be only 1 - 5 minutes.
  • a slurry (with 50 % by weight of terephthalic acid, 100 °C) resulting from re-slurrying the crystals obtained by subjecting the slurry as employed in Example 1 to a single centrifugation in accordance with the conventional practice was treated in the similar manner as described in Example 1.
  • the operation duration of the RVF until occurrence of stuffing of the filter medium was found to be 100 hours.
  • Example 2 The procedures of Example 2 were modified so that the slurry side in the RVF was maintained at the atmospheric pressure and a temperature of 110°C and the filtrate side was held at a pressure -400 mmHg lower than the atmospheric pressure and at a temperature of 90°C. An operation duration until occurrence of stuffing of the filter medium was found to be 5 hours.
  • a terephthalic acid/water slurry (terephthalic acid concentration of 40 % by weight, 150°C) obtained by purifying the crude terephthalic acid product recovered in Example 1 by an oxidation-reduction treatment was treated in a similar manner as in Example 1 to recover the refined terephthalic acid crystals.
  • the slurry side in the RVF at a pressure of 5.5 Kg/cm 2 abs. and at a temperature of 150 °C and the filtrate side at a pressure of 5.0 Kg/cm 2 abs. at a temperature of 150°C. an operation duration until occurrence of stuffing of the filter medium was found to be 250 hours.
  • Example 3 The procedures of Example 3 were modified, so that the slurry side in the RVF was maintained at atmospheric pressure at 100°C and the filtrate side was maintained at a pressure -400 mmHg lower than the atmospheric pressure at 80°C.
  • the operation duration of the RVF until stuffing of the filter medium was found to be 50 minutes.
  • the method according to the present invention is suitable for recovering crude and purified terephthalic acid crystalline products as explained above. It is applicable also for recovering other crystalline products in general from slurries containing them, such as, those in the production of hydroquinone, resorcin and so on.

Abstract

The invention relates to a process for efficiently recovering crystals from slurry for a long time by feeding a slurry to a rotary vacuum filter, filtering with suction while rotating a cylindrical filtering member, washing and again filtering with suction, which comprises applying pressure to the slurry side so as to keep the temperature and pressure at levels not making the filtrate from the rotary vacuum filter supersaturated. This process enables prevention of clogging of the filtering member due to precipitation of crystals from the mother liquor side or due to an increase in viscosity, and efficient recovery of crystals from the slurry for a long period of time. This process is adapted for recovery of crystals of crude or purified terephthalic acid, and is also applicable to recovery of crystals in general, such as hydroquinone or resorcinol, from slurry.

Description

    Technical Field of the Invention
  • The present invention relates to a method for recovering crystals from a slurry containing crystals of, such as terephthalic acid.
    • Background Art
  • In the production of terephthalic acid by a liquid phase oxidation of paradialkylbenzene, terephthalic acid produced will deposit within the mother liquor as crystals forming a slurry containing crystals of terephthalic acid. By separating the crystals out of this slurry, a crude product of terephthalic acid is obtained. After dissolution of the resulting crude crystals and subjecting to purification by treatments by oxidation, reduction and so on, terephthalic acid is caused to deposit as crystals to form a slurry containing the crystals. By separating the crystals from this slurry, purified terephthalic acid is obtained.
  • In either of the above-mentioned cases, the slurry has heretofore been subjected to procedures of separating the crystals by filtration or by centrifugation, washing the so separated crystals by re-slurrying in a wash liquor, separating again the crystals from this re-slurry and, if necessary, repeating these operations. Such a conventional technique reveals disadvantages that the procedures are complicated and that a larger apparatus has to be installed therefor.
  • As an alternative for this technique, a method had been proposed in which a sucking filtration, filter cake washing and a further sucking filtration are successively effected within a rotary vacuum filter (designated hereinafter as RVF). In this technique, a sequence of operations of a sucking filtration, a filter cake washing, a further sucking filtration and removal of the filtered cake is realized in succession while rotating a cylindrical filter medium (filter cloth), wherein an ordinary pressure prevails outside the filter medium and the filtration pressure is attained by sucking out of the internal of the filter medium. However, this technique has a disadvantage that the stuffing or blockage of the filter medium proceeds quite steeply and the operation of apparatus is forced to be interrupted.
  • The object of the present invention is to obviate the disadvantage mentioned above and to propose a novel method for recovering crystals from a slurry under the use of RVF, which enables to recover the crystals by effecting a sequence of operations of filtration, washing and further filtration without suffering from stuffing of the filter medium.
    • Disclosure of the Invention
  • The present invention proposes a method for recovering crystals from a slurry by supplying the slurry to a rotary vacuum filter while rotating a cylindrical filter medium thereof to effect a sequence of operations of sucking filtration, washing and further sucking filtration, said method comprising conducting a sucking filtration while pressurizing the slurry side so as to maintain such a temperature and pressure that the filtrate of the rotary vacuum filter will not reach a condition of supersaturation.
  • Investigating the cause for the stuffing of filter medium upon recovery of crystals using an RVF, it has now been discovered that this is due to deposition, together with an increase in the viscosity of the slurry, of the solute from the mother liquor onto the surfaces of the filter medium resulting from supersaturation of the mother liquor reached by a decrease in the temperature of the slurry caused by the sucking of the filter drum. Therefore, the present invention incorporates a sucking filtration under a pressurized condition, in order to avoid the supersaturation of the mother liquor as mentioned above.
  • Thus, according to the present invention, the sucking filtration in the RVF is carried out while pressurizing the slurry side on the rotating filter medium so as to maintain such a temperature and pressure that the filtrate of the rotary vacuum filter will not reach a condition of supersaturation. In this manner, a premature stuffing of the filter medium due to the deposition of crystals from the mother liquor together with an increase in the viscosity of the-slurry is eliminated and the crystals can be recovered from the slurry at higher efficiency over a considerable long period of time.
    • Brief Description of the Drawings
    • Fig 1 shows a flow sheet of one embodiment of the method according to the present invention.
    • Fig. 2 is a schematic sectional view of the rotary vacuum filter.
    The Best Mode of Realization of the Invention
  • Below, the method according to the present invention will be described concretely with reference to the Drawings appended.
  • In the Figs. appended, numeral 1 indicates an RVF housed by a casing 2 in which a horizontal cylindrical filter medium 3 is disposed in freely rotatable manner. The lower part of the filter medium 3 is soaked in a sump of slurry 4 formed inside the lower part of the casing 2 to form a filtering region 5, inside which there is provided an exhaustion unit 8 for sucking out internal gas 7 and the accumulated filtrate 6. Opposing to the upper portion of the filter medium, there is provided a spray unit 10 for spraying the wash liquor onto the filtered cake 9. Corresponding thereto, the filter medium 3 has a washing region 11 and, subsequent thereto, a de-liquoring region 12, inside which there is provided a collecting section 13 where the wash liquor is collected. In the further front and inside of the filter medium 3 are provided a blowing horn 14 and a gas seal 14a to be served for the removal of filtered cake 9 and the corresponding portion of the filter medium is constituted as cake removal zone 15, inside which is arranged a gas supply part 16 for supplying a blowing gas, such as nitrogen or so on. 17 denotes a slurry supply inlet, 18 a slurry accumulater, 19 a cake accumulator and 20 a gas inlet for regulating the pressure.
  • 21 is a slurry reservoir from which the slurry is supplied to the RVF 1 at the slurry supply inlet 17 by a pump 22, while recirculating the slurry via the slurry accumulator 18. 23 is a control valve for keeping the liquid level in the slurry reservoir 21 constant and 24 is a control valve for maintaining the liquid level in the slurry accumulator 18 fixedly. 25 is a control exhaustion valve for exhausting the gas so as to maintain the internal pressure in the slurry reservoir 21. 26 is a condenser. 27 is a slurry make-up inlet.
  • 28 is a wash waste tank in which the spent wash liquor collected in the collecting section 13 is accumulated and from which it is exhausted out of the system by a pump 29. 30 is a control valve operative so as to keep the liquid level in the wash waste tank 28 constant. 31 is a filtrate storage receiving the filtrate 6 and the gas 7 sucked out from the exhaustion unit 8 and exhausting the filtrate 6 by a pump 32. 33 is a level control valve operative for maintaining a constant liquid level in the filtrate storage 31.
  • The gas in the wash waste tank 28 and in the filtrate storage 31 is passed to a condenser 34 to effect condensation, the drain of which is separated by a drain separator 35 and the liquid phase separated is turned back to the filtrate storage 31, whereupon the gas is compressed by a compressor 36 and is then supplied to the gas inlet 20 as the pressure control gas. 37 is a pressure control valve operative so as to maintain a constant pressure of the pressure control gas. 38 is a drier which serves for drying the cake 9 discharged from the cake accumulator 19 via two closure valve means 39 and 40, from which it is taken out as refined crystals (product of manufacture).
  • For effecting the method for recovering the crystals, the slurry 4 stored in the slurry reservoir 21 is supplied to the sump of RVF 1 by a pump 22 and the filter medium 3 is caused to rotate so as to effect, in succession, the steps of sucking filtration, washing, sucking de-liquoring and removal of the washed cake. Here, the compressed gas for controlling the filtration pressure is supplied via the gas inlet 20 to pressurize the slurry side 4, in order to maintain the filtrate 6 at such a pressure and temperature that no supersaturation thereof occurs, while sucking out the filtrate 6 and the gas 7 from the exhaustion unit 8 to effect sucking filtration in the filtering region 5. Here, the pressure on the side of the slurry corresponds to the sum of the filtering pressure drop and the pressure on the side of the filtrate. A sucking filtration is realized thereby, wherein the crystals suspending in the slurry 4 are retained on the rotating filter medium 3 and forms a layer of filtered cake 9 guided upwards, while a part of the slurry 4 is recirculated from the slurry accumulator 18 to the slurry reservoir 21.
  • Filtered cake 9 is washed in the washing region 11 by a wash liquor sprayed from the spray unit 10 and passes then to the de-liquoring region 12, where the wash liquor is removed, and turns downwards. In the cake removal zone 15, a blowing gas is supplied to the gas supply part 16 and is caused to blow out from the blowing horn 14 to remove the cake 9.
  • The filtrate 6 and the gas 7 sucked out of the exhaustion unit 8 are introduced into the filtrate storage 31, from which the filtrate 6 is exhausted by the pump 32.
  • The spent wash liquor exhausted from the collecting section 13 is introduced into the wash waste tank 28, from which it is discharged out of the system by the pump 29.
  • The gas accumulating in the wash waste tank 28 and in the filtrate storage 31 is passed via the condenser 34 to the drain separator 35, whereupon the gas separated from the condensed drain is compressed by the compressor 36 and the thus compressed gas is served for the filtration pressure control gas and is supplied to the gas inlet 20 to pressurize the side of the slurry 4 of the RVF 1.
  • By maintaining the filterate 6 at such a pressure and temperature that no supersaturation thereof occurs upon sucking from the exhaustion unit 8 by pressurizing the slurry side of the RVF 1 by a pressure control gas, there occurs no supersaturation either in the slurry 4 and in the filtrate 6, so that no deposition of crystals nor increase in the viscosity of the slurry occurs and, thus, the problem of stuffing of the filter medium 3 is solved.
  • It is essential to adjust the internal pressure so as to avoid any deposition of the solute of the same material with the crystals to be recovered as well as of any impurity in the mother liquor. While the internal pressure on the side of the filtrate may occasionally reach a superatmospheric pressure, the filtration is effected even in such a case by the pressure difference between the slurry side and the filtrate side.
  • If the deposition of crystals is considerable due to the decrease in the temperature of the slurry by the heat dissipation from RVF 1, it is preferable to insulate the system and, if necessary, to maintain the temperature by installing a heat exchanger or the like.
  • The cake 9 removed in the cake removal zone 15 is taken out through the two closure valves 39 and 40 and is dried in the drier 38, before it is recovered therefrom as purified crystals (product of manufacture).
  • In the following, description is directed to Examples of the present invention.
    • Example 1
  • A slurry of terephthalic acid/acetic acid (with 40 % by weight of terephthalic acid, at 120 1C) resulting from an industrial production of terephthalic acid was treated by the method illustrated in the appended Figs. to recover crude terephthalic acid crystals. Here, the slurry side in the RVF was maintained at a pressure of 1.5 Kg/cm2 abs. at 120 °C and the filtrate side at a pressure of 1 Kg/cm2 abs. at 120 °C. The operation duration of the RVF until occurrence of stuffing of the filter medium was found to be 50 hours.
    • Comparison Example 1
  • The procedures of Example 1 were repeated under a modification of the condition that the slurry side in the RVF 1 was maintained at the atmospheric pressure and at a temperature of 120°C and the filtrate side was held at a pressure -400 mmHg lower than the atmospheric pressure and at a temperature of 100 °C. The operation duration of the RVF until occurrence of stuffing of the filter medium was found to be only 1 - 5 minutes.
    • Example 2
  • A slurry (with 50 % by weight of terephthalic acid, 100 °C) resulting from re-slurrying the crystals obtained by subjecting the slurry as employed in Example 1 to a single centrifugation in accordance with the conventional practice was treated in the similar manner as described in Example 1. By maintaining the slurry side in the RVF at a pressure of 1.0 Kg/cm2 abs. and a temperature of 110°C and the filtrate side at a pressure of 0.5 Kg/cm2 abs. and a temperature of 110°C. the operation duration of the RVF until occurrence of stuffing of the filter medium was found to be 100 hours.
    • Comparison Example 2
  • The procedures of Example 2 were modified so that the slurry side in the RVF was maintained at the atmospheric pressure and a temperature of 110°C and the filtrate side was held at a pressure -400 mmHg lower than the atmospheric pressure and at a temperature of 90°C. An operation duration until occurrence of stuffing of the filter medium was found to be 5 hours.
    • Example 3
  • A terephthalic acid/water slurry (terephthalic acid concentration of 40 % by weight, 150°C) obtained by purifying the crude terephthalic acid product recovered in Example 1 by an oxidation-reduction treatment was treated in a similar manner as in Example 1 to recover the refined terephthalic acid crystals. By maintaing the slurry side in the RVF at a pressure of 5.5 Kg/cm2 abs. and at a temperature of 150 °C and the filtrate side at a pressure of 5.0 Kg/cm2 abs. at a temperature of 150°C. an operation duration until occurrence of stuffing of the filter medium was found to be 250 hours.
    • Comparison.Example 3
  • The procedures of Example 3 were modified, so that the slurry side in the RVF was maintained at atmospheric pressure at 100°C and the filtrate side was maintained at a pressure -400 mmHg lower than the atmospheric pressure at 80°C. The operation duration of the RVF until stuffing of the filter medium was found to be 50 minutes.
    • Applicabilities of the Invention in Industry
  • The method according to the present invention is suitable for recovering crude and purified terephthalic acid crystalline products as explained above. It is applicable also for recovering other crystalline products in general from slurries containing them, such as, those in the production of hydroquinone, resorcin and so on.

Claims (1)

  1. A method for recovering crystals from a slurry by supplying the slurry to a rotary vacuum filter while rotating a cylindrical filter medium thereof to effect a sequence of operations of sucking filtration, washing and further sucking filtration, said method comprising conducting a sucking filtration while pressurizing the slurry side so as to maintain such a temperature and pressure that the filtrate of the rotary vacuum filter will not reach a condition of supersaturation.
EP89906439A 1988-05-27 1989-05-26 Process for recovering crystals from slurry Expired - Lifetime EP0406424B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP129540/88 1988-05-27
JP63129540A JP2595657B2 (en) 1988-05-27 1988-05-27 How to recover crystals from a slurry
PCT/JP1989/000529 WO1989011323A1 (en) 1988-05-27 1989-05-26 Process for recovering crystals from slurry

Publications (3)

Publication Number Publication Date
EP0406424A1 true EP0406424A1 (en) 1991-01-09
EP0406424A4 EP0406424A4 (en) 1991-08-07
EP0406424B1 EP0406424B1 (en) 1995-01-25

Family

ID=15012051

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89906439A Expired - Lifetime EP0406424B1 (en) 1988-05-27 1989-05-26 Process for recovering crystals from slurry

Country Status (11)

Country Link
US (1) US5093001A (en)
EP (1) EP0406424B1 (en)
JP (1) JP2595657B2 (en)
KR (2) KR920002805B1 (en)
CN (1) CN1026318C (en)
AT (1) ATE117573T1 (en)
CA (1) CA1320148C (en)
DE (1) DE68920869T2 (en)
RU (1) RU2035966C1 (en)
UA (1) UA8356A1 (en)
WO (1) WO1989011323A1 (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993024440A1 (en) * 1992-05-29 1993-12-09 Imperial Chemical Industries Plc Process for the production of purified terephthalic acid
EP0630673A1 (en) * 1993-05-24 1994-12-28 Mitsui Petrochemical Industries, Ltd. Method and apparatus for recovering crystals from slurry
US5527957A (en) * 1991-03-07 1996-06-18 Imperial Chemical Industries Plc Process for the production of terephthalic acid
EP1170280A2 (en) * 2000-07-05 2002-01-09 Mitsubishi Gas Chemical Company, Inc. Process for recovering crystals from a slurry
WO2007103068A1 (en) * 2006-03-01 2007-09-13 Eastman Chemical Company Methods and apparatus for isolating carboxylic acid
US7847121B2 (en) 2006-03-01 2010-12-07 Eastman Chemical Company Carboxylic acid production process
US7863483B2 (en) 2006-03-01 2011-01-04 Eastman Chemical Company Carboxylic acid production process

Families Citing this family (31)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9302333D0 (en) * 1993-02-05 1993-03-24 Ici Plc Filtration process
US5470473A (en) * 1994-02-17 1995-11-28 Baker Hughes Incorporated Rotary vacuum filtration drum with valved hopper cake treatment means
WO1998018750A1 (en) * 1996-10-30 1998-05-07 Mitsui Chemicals, Inc. Process for preparing aromatic dicarboxylic acids
JPH11179115A (en) * 1997-12-24 1999-07-06 Mitsui Chem Inc Method and apparatus for recovering crystal from slurry
EP1150341A4 (en) * 1998-12-28 2005-06-08 Hitachi Chemical Co Ltd Materials for polishing liquid for metal, polishing liquid for metal, method for preparation thereof and polishing method using the same
EP1225964A1 (en) * 1999-05-24 2002-07-31 Baker Hughes Incorporated Pressure filtration device and method employing a depressurizing chamber and material transport
ES2320321T3 (en) 2000-03-17 2009-05-21 LG HOUSEHOLD & HEALTH CARE LTD. PATCHES FOR WHITENING TEETH.
US6655531B1 (en) 2000-05-23 2003-12-02 Baker Hughes Incorporated Pressure filtration device
KR100423938B1 (en) * 2001-11-29 2004-03-22 삼성정밀화학 주식회사 A method for filtering method of fibrous compound and an apparatus thereof
AU2003280809A1 (en) * 2002-11-14 2004-06-03 Mitsubishi Chemical Corporation Process for producing terephthalic acid
KR20040048106A (en) * 2002-12-02 2004-06-07 이재철 A pressurized continuous filtering method and device
JP4804776B2 (en) * 2005-03-22 2011-11-02 三井化学株式会社 Method for recovering crystals from slurry
JP2007021453A (en) * 2005-07-21 2007-02-01 Mitsubishi Kakoki Kaisha Ltd Remaining filtrate recovery system used for rotary strainer and method for recovering remaining filtrate
US9144750B2 (en) 2006-06-12 2015-09-29 Mitsubishi Gas Chemical Company, Ltd. Method of replacing dispersion medium and apparatus therefor
JP5291459B2 (en) * 2006-06-12 2013-09-18 三菱瓦斯化学株式会社 Dispersion medium replacement method
RU2009149616A (en) * 2007-05-31 2011-07-10 Дау Илалия С.Р.Л. (It) IMPROVED METHOD FOR REMOVING TERPHTHALIC ACID
RU2463096C2 (en) * 2007-12-20 2012-10-10 Хитачи Плант Текнолоджиз, Лтд. Method of crystalline suspension filtration
WO2009081458A1 (en) * 2007-12-20 2009-07-02 Hitachi Plant Technologies, Ltd. Method of filtering crystallization slurry
WO2010119484A1 (en) * 2009-04-16 2010-10-21 株式会社日立プラントテクノロジー Method for recovering crystals from a crystallization slurry
US8309711B2 (en) * 2009-08-07 2012-11-13 Corn Products Development Inc. Filtration of corn starch followed by washing and collection of the resultant corn starch cake
CN101624342B (en) * 2009-08-13 2012-10-31 中国纺织工业设计院 Method and system for separating and filtering CTA in preparation of pure terephthalic acid
KR101135940B1 (en) 2009-10-29 2012-04-18 한국전력공사 An apparatus for removing impurity of slurry
JPWO2014049793A1 (en) * 2012-09-27 2016-08-22 三菱化工機株式会社 Operation method of pressurized single chamber rotary filter
CN103386227B (en) * 2013-07-08 2015-05-27 嘉兴石化有限公司 Improvement on pressure filter for producing purified terephthalic acid
CA2927961C (en) 2013-11-08 2017-05-16 Hugues Wanlin Rotary vacuum and screen system and methods for separating solids and liquids
PL3089804T3 (en) * 2013-12-31 2021-12-13 Ineos Us Chemicals Company Solid-liquid separations with a no-dry rotary pressure filter
CN106573188B (en) * 2014-07-25 2019-06-14 Bp北美公司 Rotary pressure filter apparatus with reduced pressure oscillation
CN104174221B (en) * 2014-09-04 2016-06-01 南阳鑫子源石油石化技术装备有限公司 Rotary drum pressure mud system
EP3292898A1 (en) * 2016-09-12 2018-03-14 Sulzer Chemtech AG Wash column apparatus with a static grid element for the use in a suspension crystallization process
SE542326C2 (en) * 2018-06-21 2020-04-14 Valmet Oy Vacuum filter
EP4021881B1 (en) * 2019-08-28 2023-05-10 Koch Technology Solutions UK Limited Apparatus for purifying terephthalic acid

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE705139C (en) * 1938-11-16 1941-04-18 Johannes Wiebe Process for operating rotary cell filters

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5328421B2 (en) * 1973-05-15 1978-08-15
US4263148A (en) * 1979-04-09 1981-04-21 Earth Sciences, Inc. Process for removing humic matter from phosphoric acid solutions
SU1165430A1 (en) * 1982-11-17 1985-07-07 Всесоюзный научно-исследовательский и проектный институт галургии Method of dehydrating suspensions

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE705139C (en) * 1938-11-16 1941-04-18 Johannes Wiebe Process for operating rotary cell filters

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Perry's Chemical Engineers' Handbook; Robert H. Perry, Don Green; 6th edition;page 19-80 *
See also references of WO8911323A1 *

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5679846A (en) * 1991-03-07 1997-10-21 Imperial Chemical Industries Plc Process for the production of terephalic acid
US5877346A (en) * 1991-03-07 1999-03-02 E. I. Du Pont De Nemours And Company Process for the production of terephthalic acid
US5527957A (en) * 1991-03-07 1996-06-18 Imperial Chemical Industries Plc Process for the production of terephthalic acid
US5563293A (en) * 1991-03-07 1996-10-08 Imperial Chemical Industries Plc Process for the production of terephthalic acid
US5583254A (en) * 1992-05-29 1996-12-10 Turner; John A. Process for the production of purified terephthalic acid
AU681078B2 (en) * 1992-05-29 1997-08-21 E.I. Du Pont De Nemours And Company Process for the production of purified terephthalic acid
WO1993024440A1 (en) * 1992-05-29 1993-12-09 Imperial Chemical Industries Plc Process for the production of purified terephthalic acid
US5676847A (en) * 1993-05-24 1997-10-14 Mitsui Petrochemical Industries, Ltd. Method for recovering crystals from slurry with wash water recycle means
EP0630673A1 (en) * 1993-05-24 1994-12-28 Mitsui Petrochemical Industries, Ltd. Method and apparatus for recovering crystals from slurry
EP1170280A2 (en) * 2000-07-05 2002-01-09 Mitsubishi Gas Chemical Company, Inc. Process for recovering crystals from a slurry
EP1170280A3 (en) * 2000-07-05 2003-05-07 Mitsubishi Gas Chemical Company, Inc. Process for recovering crystals from a slurry
KR100738737B1 (en) * 2000-07-05 2007-07-12 미츠비시 가스 가가쿠 가부시키가이샤 Process for recovering crystals from a slurry
WO2007103068A1 (en) * 2006-03-01 2007-09-13 Eastman Chemical Company Methods and apparatus for isolating carboxylic acid
US7462736B2 (en) 2006-03-01 2008-12-09 Eastman Chemical Company Methods and apparatus for isolating carboxylic acid
US7847121B2 (en) 2006-03-01 2010-12-07 Eastman Chemical Company Carboxylic acid production process
US7863483B2 (en) 2006-03-01 2011-01-04 Eastman Chemical Company Carboxylic acid production process

Also Published As

Publication number Publication date
CN1039580A (en) 1990-02-14
CN1026318C (en) 1994-10-26
EP0406424A4 (en) 1991-08-07
JP2595657B2 (en) 1997-04-02
WO1989011323A1 (en) 1989-11-30
KR920002805B1 (en) 1992-04-04
ATE117573T1 (en) 1995-02-15
RU2035966C1 (en) 1995-05-27
CA1320148C (en) 1993-07-13
EP0406424B1 (en) 1995-01-25
US5093001A (en) 1992-03-03
DE68920869D1 (en) 1995-03-09
DE68920869T2 (en) 1995-05-24
UA8356A1 (en) 1996-03-29
JPH01299618A (en) 1989-12-04
KR900701365A (en) 1990-12-01

Similar Documents

Publication Publication Date Title
EP0406424A1 (en) Process for recovering crystals from slurry
EP0754673B1 (en) Process for the production of terephthalic acid
EP0682554B2 (en) Filtration process
JP4243912B2 (en) Method for recovering crystals from slurry
US6033579A (en) Red mud dewatering and washing process
US20030004372A1 (en) Process for the recovery of crude terephthalic acid (cta)
CN1085889A (en) The preparation method of refining terephthalic acid
US4443421A (en) Process for removing particulate impurities from aqueous phosphoric acid
CN100509746C (en) Method of separating and purifying terephthalic acid
CN1554637A (en) Separative purifying method for terephthalic acid
JP3859178B2 (en) Method and apparatus for producing high-purity aromatic dicarboxylic acid
KR970004909B1 (en) Rotary vacuum filter
KR970006318B1 (en) Freeze concentration system and method
JP2595657C (en)
PL190036B1 (en) Method of purifying melamine during its recrystallisation process and apparatus therefor

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19900119

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

A4 Supplementary search report drawn up and despatched

Effective date: 19910617

AK Designated contracting states

Kind code of ref document: A4

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

17Q First examination report despatched

Effective date: 19920721

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19950125

Ref country code: CH

Effective date: 19950125

REF Corresponds to:

Ref document number: 117573

Country of ref document: AT

Date of ref document: 19950215

Kind code of ref document: T

EAL Se: european patent in force in sweden

Ref document number: 89906439.8

ET Fr: translation filed
ITF It: translation for a ep patent filed

Owner name: ST. DR. CAVATTONI ING. A. RAIMONDI

REF Corresponds to:

Ref document number: 68920869

Country of ref document: DE

Date of ref document: 19950309

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
REG Reference to a national code

Ref country code: FR

Ref legal event code: CD

NLT1 Nl: modifications of names registered in virtue of documents presented to the patent office pursuant to art. 16 a, paragraph 1

Owner name: MITSUI CHEMICALS, INC.

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19990414

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19990511

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 19990512

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19990526

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: LU

Payment date: 19990528

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19990531

Year of fee payment: 11

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000526

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000526

Ref country code: AT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000526

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000527

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20001201

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20000526

EUG Se: european patent has lapsed

Ref document number: 89906439.8

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20010131

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee

Effective date: 20001201

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20040603

Year of fee payment: 16

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 20040715

Year of fee payment: 16

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 20050526

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: BE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20050531

BERE Be: lapsed

Owner name: *MITSUI CHEMICALS INC.

Effective date: 20050531

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20051201

BERE Be: lapsed

Owner name: *MITSUI CHEMICALS INC.

Effective date: 20050531